Merge branch 'issues'

# Conflicts:
#	mdl/grammar/parser/MDLParser.interp
#	mdl/grammar/parser/mdl_parser.go

Author: ako

.claude/skills/mendix/alter-page.md

@@ -126,6 +126,30 @@ REPLACE footer1 WITH {
 
 Replaces the target widget with one or more new widgets. The new widgets use the same syntax as `CREATE PAGE`.
 
+### DataGrid Column Operations
+
+DataGrid2 columns are addressable using dotted notation: `gridName.columnName`. The column name is derived from the attribute short name or caption (same as shown by `DESCRIBE PAGE`).
+
+```sql
+-- SET a column property
+SET Caption = 'Product SKU' ON dgProducts.Code
+
+-- DROP a column
+DROP WIDGET dgProducts.OldColumn
+
+-- INSERT a column after an existing one
+INSERT AFTER dgProducts.Price {
+  COLUMN Margin (Attribute: Margin, Caption: 'Margin')
+}
+
+-- REPLACE a column
+REPLACE dgProducts.Description WITH {
+  COLUMN Notes (Attribute: Notes, Caption: 'Notes')
+}
+```
+
+To discover column names, run `DESCRIBE PAGE Module.PageName` and look at the COLUMN names inside the DATAGRID.
+
 ### ADD Variables - Add a Page Variable
 
 ```sql

docs-site/src/examples/alter-page.md

@@ -82,6 +82,31 @@ ALTER PAGE CRM.Customer_Edit {
 };
 ```
 
+## Modify DataGrid Columns
+
+Target columns using dotted notation `gridName.columnName`:
+
+```sql
+-- Add a column
+ALTER PAGE CRM.Customer_List {
+  INSERT AFTER dgCustomers.Email {
+    COLUMN Phone (Attribute: Phone, Caption: 'Phone')
+  }
+};
+
+-- Remove a column
+ALTER PAGE CRM.Customer_List {
+  DROP WIDGET dgCustomers.OldNotes
+};
+
+-- Rename a column header
+ALTER PAGE CRM.Customer_List {
+  SET Caption = 'E-mail Address' ON dgCustomers.Email
+};
+```
+
+Use `DESCRIBE PAGE CRM.Customer_List` to discover column names.
+
 ## Works on Snippets Too
 
 ```sql

docs-site/src/language/alter-page.md

@@ -213,14 +213,32 @@ ALTER PAGE MyModule.Order_Edit {
 };
 ```
 
-### Add a DataGrid Column
+### DataGrid Column Operations
 
-Since DataGrid columns are part of the widget tree, use INSERT to add columns:
+DataGrid2 columns are addressable using dotted notation: `gridName.columnName`. Use `DESCRIBE PAGE` to discover column names (derived from the attribute short name or caption).
 
 ```sql
+-- Add a column after an existing one
 ALTER PAGE MyModule.Customer_Overview {
-  INSERT AFTER colEmail {
-    COLUMN colPhone (Attribute: Phone, Caption: 'Phone')
+  INSERT AFTER dgCustomers.Email {
+    COLUMN Phone (Attribute: Phone, Caption: 'Phone')
+  }
+};
+
+-- Remove a column
+ALTER PAGE MyModule.Customer_Overview {
+  DROP WIDGET dgCustomers.OldColumn
+};
+
+-- Change a column's caption
+ALTER PAGE MyModule.Customer_Overview {
+  SET Caption = 'E-mail Address' ON dgCustomers.Email
+};
+
+-- Replace a column
+ALTER PAGE MyModule.Customer_Overview {
+  REPLACE dgCustomers.Notes WITH {
+    COLUMN Description (Attribute: Description, Caption: 'Description')
   }
 };
 ```

docs-site/src/reference/page/alter-page.md

@@ -76,6 +76,19 @@ Removes one or more widgets by name. The widget and all its children are removed
 
 Replaces a widget (and its entire subtree) with one or more new widgets.
 
+### DataGrid Column Operations
+
+DataGrid2 columns are addressable using dotted notation: `gridName.columnName`. The column name matches the name shown by `DESCRIBE PAGE` (derived from the attribute short name or caption).
+
+All four operations (SET, INSERT, DROP, REPLACE) support dotted column references:
+
+```sql
+SET Caption = 'Product SKU' ON dgProducts.Code
+DROP WIDGET dgProducts.OldColumn
+INSERT AFTER dgProducts.Price { COLUMN Margin (Attribute: Margin) }
+REPLACE dgProducts.Description WITH { COLUMN Notes (Attribute: Notes) }
+```
+
 ### SET Layout
 
 Changes the page's layout without rebuilding the widget tree. Placeholder names are auto-mapped by default. If the new layout has different placeholder names, use `MAP` to specify the mapping.

docs/01-project/MDL_QUICK_REFERENCE.md

@@ -629,6 +629,9 @@ Modify an existing page or snippet's widget tree in-place without full `CREATE O
 | Drop widgets | `DROP WIDGET name1, name2` | Remove widgets by name |
 | Replace widget | `REPLACE widgetName WITH { widgets }` | Replace widget subtree |
 | Pluggable prop | `SET 'showLabel' = false ON cbStatus` | Quoted name for pluggable widgets |
+| Set column prop | `SET Caption = 'New' ON dgGrid.colName` | Dotted ref targets DataGrid column |
+| Drop column | `DROP WIDGET dgGrid.colName` | Remove a DataGrid column |
+| Insert column | `INSERT AFTER dgGrid.colName { COLUMN ... }` | Add column to DataGrid |
 | Add variable | `ADD Variables $name: Type = 'expr'` | Add a page variable |
 | Drop variable | `DROP Variables $name` | Remove a page variable |
 | Set layout | `SET Layout = Module.LayoutName` | Change page layout, auto-maps placeholders |

mdl-examples/doctype-tests/03-page-examples.mdl

@@ -2259,6 +2259,20 @@ ALTER PAGE PgTest.P033b_DataGrid_ColumnProperties {
   SET Layout = Atlas_Core.Atlas_TopBar;
 };
 
+-- MARK: ALTER PAGE DataGrid Column Operations
+
+-- =============================================================================
+-- ALTER PAGE - DataGrid Column Operations (dotted widget references)
+-- =============================================================================
+--
+-- DataGrid2 columns are addressable using gridName.columnName syntax.
+-- Column names are derived from the attribute short name or caption.
+
+-- DROP a column by dotted reference
+ALTER PAGE PgTest.P033b_DataGrid_ColumnProperties {
+  DROP WIDGET dgProducts.Description
+};
+
 -- MARK: Conditional Visibility/Editability and Responsive Widths
 
 -- =============================================================================

mdl/ast/ast_alter_page.go

@@ -20,34 +20,55 @@ type AlterPageOperation interface {
 	isAlterPageOperation()
 }
 
-// SetPropertyOp represents: SET prop = value ON widgetName
-// or SET prop = value (page-level, WidgetName empty)
+// WidgetRef represents a widget reference, optionally with a sub-element path.
+// Plain: "btnSave" (Widget="btnSave", Column="")
+// Dotted: "dgProducts.Name" (Widget="dgProducts", Column="Name")
+type WidgetRef struct {
+	Widget string // widget name (always set)
+	Column string // column name within widget (empty for plain widget refs)
+}
+
+// Name returns the full reference string for error messages.
+func (r WidgetRef) Name() string {
+	if r.Column != "" {
+		return r.Widget + "." + r.Column
+	}
+	return r.Widget
+}
+
+// IsColumn returns true if this is a column reference (dotted path).
+func (r WidgetRef) IsColumn() bool {
+	return r.Column != ""
+}
+
+// SetPropertyOp represents: SET prop = value ON widgetRef
+// or SET prop = value (page-level, Target.Widget empty)
 type SetPropertyOp struct {
-	WidgetName string                 // empty for page-level SET
+	Target     WidgetRef              // empty Widget for page-level SET
 	Properties map[string]interface{} // property name -> value
 }
 
 func (s *SetPropertyOp) isAlterPageOperation() {}
 
-// InsertWidgetOp represents: INSERT AFTER/BEFORE widgetName { widgets }
+// InsertWidgetOp represents: INSERT AFTER/BEFORE widgetRef { widgets }
 type InsertWidgetOp struct {
-	Position   string // "AFTER" or "BEFORE"
-	TargetName string // widget to insert relative to
-	Widgets    []*WidgetV3
+	Position string    // "AFTER" or "BEFORE"
+	Target   WidgetRef // widget/column to insert relative to
+	Widgets  []*WidgetV3
 }
 
 func (s *InsertWidgetOp) isAlterPageOperation() {}
 
-// DropWidgetOp represents: DROP WIDGET name1, name2, ...
+// DropWidgetOp represents: DROP WIDGET ref1, ref2, ...
 type DropWidgetOp struct {
-	WidgetNames []string
+	Targets []WidgetRef
 }
 
 func (s *DropWidgetOp) isAlterPageOperation() {}
 
-// ReplaceWidgetOp represents: REPLACE widgetName WITH { widgets }
+// ReplaceWidgetOp represents: REPLACE widgetRef WITH { widgets }
 type ReplaceWidgetOp struct {
-	WidgetName string
+	Target     WidgetRef
 	NewWidgets []*WidgetV3
 }
 

mdl/executor/alter_page_test.go

@@ -95,7 +95,7 @@ func TestApplyDropWidget_Single(t *testing.T) {
 	w3 := makeWidget("txtPhone", "Pages$TextBox")
 	rawData := makeRawPage(w1, w2, w3)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"txtEmail"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "txtEmail"}}}
 	if err := applyDropWidget(rawData, op); err != nil {
 		t.Fatalf("applyDropWidget failed: %v", err)
 	}
@@ -126,7 +126,7 @@ func TestApplyDropWidget_Multiple(t *testing.T) {
 	w3 := makeWidget("c", "Pages$TextBox")
 	rawData := makeRawPage(w1, w2, w3)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"a", "c"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "a"}, {Widget: "c"}}}
 	if err := applyDropWidget(rawData, op); err != nil {
 		t.Fatalf("applyDropWidget failed: %v", err)
 	}
@@ -150,7 +150,7 @@ func TestApplyDropWidget_NotFound(t *testing.T) {
 	w1 := makeWidget("txtName", "Pages$TextBox")
 	rawData := makeRawPage(w1)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"nonexistent"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "nonexistent"}}}
 	err := applyDropWidget(rawData, op)
 	if err == nil {
 		t.Fatal("Expected error for nonexistent widget")
@@ -163,7 +163,7 @@ func TestApplyDropWidget_Nested(t *testing.T) {
 	container := makeContainerWidget("ctn1", inner1, inner2)
 	rawData := makeRawPage(container)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"txtInner1"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "txtInner1"}}}
 	if err := applyDropWidget(rawData, op); err != nil {
 		t.Fatalf("applyDropWidget failed: %v", err)
 	}
@@ -186,7 +186,7 @@ func TestApplySetProperty_Name(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "txtOld",
+		Target: ast.WidgetRef{Widget: "txtOld"},
 		Properties: map[string]interface{}{
 			"Name": "txtNew",
 		},
@@ -211,7 +211,7 @@ func TestApplySetProperty_ButtonStyle(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "btnSave",
+		Target: ast.WidgetRef{Widget: "btnSave"},
 		Properties: map[string]interface{}{
 			"ButtonStyle": "Success",
 		},
@@ -234,7 +234,7 @@ func TestApplySetProperty_WidgetNotFound(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "nonexistent",
+		Target: ast.WidgetRef{Widget: "nonexistent"},
 		Properties: map[string]interface{}{
 			"Name": "new",
 		},
@@ -279,7 +279,7 @@ func TestApplySetProperty_PluggableWidget(t *testing.T) {
 	rawData := makeRawPage(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "cb1",
+		Target: ast.WidgetRef{Widget: "cb1"},
 		Properties: map[string]interface{}{
 			"showLabel": false,
 		},
@@ -448,7 +448,7 @@ func TestApplyDropWidget_Snippet(t *testing.T) {
 	w2 := makeWidget("txtEmail", "Pages$TextBox")
 	rawData := makeRawSnippet(w1, w2)
 
-	op := &ast.DropWidgetOp{WidgetNames: []string{"txtEmail"}}
+	op := &ast.DropWidgetOp{Targets: []ast.WidgetRef{{Widget: "txtEmail"}}}
 	if err := applyDropWidgetWith(rawData, op, findBsonWidgetInSnippet); err != nil {
 		t.Fatalf("applyDropWidgetWith failed: %v", err)
 	}
@@ -473,7 +473,7 @@ func TestApplySetProperty_Snippet(t *testing.T) {
 	rawData := makeRawSnippet(w1)
 
 	op := &ast.SetPropertyOp{
-		WidgetName: "btnAction",
+		Target: ast.WidgetRef{Widget: "btnAction"},
 		Properties: map[string]interface{}{
 			"ButtonStyle": "Danger",
 		},